No size limits, no cloud: Hands-on with BitTorrent's new file syncing software.

BitTorrent today released folder syncing software that replicates files across multiple computers using the same peer-to-peer file sharing technology that powers BitTorrent clients.

The free BitTorrent Sync application is labeled as being in the alpha stage, so it's not necessarily ready for prime-time, but it is publicly available for download and working as advertised on my home network.

BitTorrent, Inc. (yes, there is a legitimate company behind BitTorrent) took to its blog to announce the move from a pre-alpha, private program to the publicly available alpha. Additions since the private alpha include one-way synchronization, one-time secrets for sharing files with a friend or colleague, and the ability to exclude specific files and directories.

BitTorrent Sync provides "unlimited, secure file-syncing," the company said. "You can use it for remote backup. Or, you can use it to transfer large folders of personal media between users and machines; editors and collaborators. It’s simple. It’s free. It’s the awesome power of P2P, applied to file-syncing."

File transfers are encrypted, with private information never being stored on an external server or in the "cloud."

"Since Sync is based on P2P and doesn’t require a pit-stop in the cloud, you can transfer files at the maximum speed supported by your network," BitTorrent said. "BitTorrent Sync is specifically designed to handle large files, so you can sync original, high quality, uncompressed files."

In the pre-alpha testing that began in January, 20,000 users synced more than 200TB of data. BitTorrent Sync clients can be downloaded now for Windows, Macs, Linux desktops, and Linux-based network-attached storage devices. Mobile support will come later.

Setting the client up is easy. No account is required, but a randomly generated (or user-chosen) 21-byte key is needed to sync folders across computers. After installing the application and choosing a folder to sync you'll be given a string of random letters and numbers that should be typed into a second computer to sync the folder:

By default, BitTorrent Sync creates a folder named "BTSync," but you can name it whatever you'd like or choose other folders to sync. As mentioned earlier, you'll enter the secret key on a second computer to allow the two computers to sync:

I dragged a few small files into the sync folder, and they synced across my two computers just about instantaneously. Then I dragged a 3.5GB Windows 8 ISO into one of them, which of course took much longer to sync, completing in just under 10 minutes.

The BitTorrent Sync client provides a view of what your other devices are up to:

Sharing folders with another person can be achieved by right-clicking the folder within the interface pictured above in order to bring up an advanced preferences menu. From there, you can choose whether to give someone full access or read-only access, and generate secret keys for one-time uses.

BitTorrent Sync perhaps doesn't make it quite as easy to share files as cloud services like Dropbox, Google Drive, or SkyDrive do. It's also far from being the first software to sync files across devices without storing them in a cloud service. But it works well so far, and—particularly when it adds mobile capabilities—BitTorrent Sync seems destined to become a worthy addition to the rapidly expanding file sharing market.

117 Reader Comments

Does the data live anywhere other than on computers that have the secret? For example, when you add something does it send it to random other users (encrypted with the secret, presumably)?

If it doesn't, then this doesn't really duplicate DropBox, et al, for one of the prime use cases, which is having a backup in case something happens to the original files. You'll need to find another computer and specifically add it to the folder in order for that to work, which is kind of a hassle.

If it does, then this is useful for that use case but means that your computer is presumably going to be storing data for other people, which is kind of annoying.

aka it's nice to have a simple, robust tool that encrypts and can maintain data consistency across the internet without using a cloud service. I could see this being very useful as the storage limitations are your own storage medium.

Actually, on flooey's question, is it possible to sync the encrypted data with a server that doesn't have the key? That would be perfect for syncing to a server that I don't fully trust, such as a server that I can share with a few friends without sharing all my data with them.

Does the data live anywhere other than on computers that have the secret? For example, when you add something does it send it to random other users (encrypted with the secret, presumably)?

If it doesn't, then this doesn't really duplicate DropBox, et al, for one of the prime use cases, which is having a backup in case something happens to the original files. You'll need to find another computer and specifically add it to the folder in order for that to work, which is kind of a hassle.

If it does, then this is useful for that use case but means that your computer is presumably going to be storing data for other people, which is kind of annoying.

It's just on machines you sync the data across. This is a great replacement for people that used to use services like Foldershare. If you only have a few files (<5GB worth), then DropBox might be better since they have it backed up for you (also assuming you trust Dropbox with your data). This is better if you want to sync any significant amount of data that you don't want 'on the cloud'.

So is the point of this tool that you can sync to many devices without copying the data separately from one device to all the other devices? If so, it seems especially useful for certain edge cases, but not for the typical ones of backing up large amounts of data or syncing to one or 2 devices.

I'm over on the forum asking the devs "Why? and how is this different from RSync" They don't have any really good answers.

They point out with a moderately sized cloud downloads would be faster as you get some combination of upstream bandwidth. But no one is talking about what happens when a file changes. How does BT handle that? Rsync would send delta blocks. Do you need a whole new file?

For those in micro-clouds of 2 or 3 stations, there isn't much benefit.

I think you made a unit error. The screenshot was MBps, not Mbps, so the speed should have been ~50+Mbps.

Yes, you're right, changed it to the big B. Embarrassing mistake, as I am usually the one explaining the difference between bits and bytes to people I know.

Not good enough. You are still writing that it's far below your network speed. So what is your upload speed? It's kind of an important detail as to actually know how good or bad is the performance of the client.

I've been following this client for several months now. I was a former user of Windows Live Mesh solely for what this program does. You select a folder (IT CAN BE ANYWHERE - ANY NAME) and sync it to an unlimited number of computers at the exact same location on the computers.

Example: I sync a photos folder in My Pictures. It will sync across all three of my computer (or just two) in the My Pictures folder.

You don't have to drag and drop into a specified folder. It's great for my schoolwork as I now know I always have a backup available on my desktop back home (300 miles away) if something ever happened to my laptop.

I'll add a bit to the sentiment that this shouldn't be represented as an alternative to cloud-based services like DropBox. Another common use case for DropBox is accessing my files from anywhere, for example when I'm on vacation or at someone else's house. For BitTorrent Sync to be a viable replacement, I would have to leave my home computer on 24/7 and open it to the internet as a file server of sorts, which is way outside my normal usage pattern and is something I'd be hesitant to do.

I've been following this client for several months now. I was a former user of Windows Live Mesh solely for what this program does. You select a folder (IT CAN BE ANYWHERE - ANY NAME) and sync it to an unlimited number of computers at the exact same location on the computers.

The Live Mesh stuff was awesome, and I was sad to see Microsoft discontinue it. This strikes me as an excellent replacement.

Yes, Live Mesh and BitTorrent Sync sound a bit like rsync, but my understanding is that an rsync sync needs to be manually initiated and/or scheduled; it does not monitor folders for changes in real time.

Now we have a "legitimate" reason to demand that our internet providers do not block P2P traffic.

I say legitimate because until now if I have ever complained about this practice more people than I expected turn around and say: why do you need p2p? Isn't that just used by internet hackers to doenload illegal stuff? Sigh

I've been following this client for several months now. I was a former user of Windows Live Mesh solely for what this program does. You select a folder (IT CAN BE ANYWHERE - ANY NAME) and sync it to an unlimited number of computers at the exact same location on the computers.

Example: I sync a photos folder in My Pictures. It will sync across all three of my computer (or just two) in the My Pictures folder.

You don't have to drag and drop into a specified folder. It's great for my schoolwork as I now know I always have a backup available on my desktop back home (300 miles away) if something ever happened to my laptop.

It's peer-to-peer instead of client-server, so it doesn't require you to run an OwnCloud server somewhere. It syncs content directly between devices. Sounds like it would be great for real-time backup to another computer/NAS in your house, or sharing picture/video content with family members etc.

So it's like turning all your files into thousands of chunks, and then copying those chunks to little USB thumb drives in a way that makes any one chunk appear on several drives. Then you divide all those USB thumb drives amongst all the people in your neighborhood.

Not quite. It starts out like that, but then all those USB flash drives get shared amongst everyone else who got a flash drive until each person has a full copy of the original set of files.

I think many people are missing the point. I share many work-related files with a large number of colleagues. Currently these are stored on a central server. We can't use (variants of) Dropbox for security reasons. If we were to use BTSync I see two immediate benefits: speed (the more users, the faster) and not having to rely on third parties for storage or the IT department for setting up a local cloud.

Edit: I realize that security with P2P is only as good as the least trustworthy peer...

My God people why does everyone complain about the lack of a backup? You do realize you are talking about two distinct functions right? Backup and sharing. If you REALLY want a backup make a git repository and make sync that. Or create copies of things you want backed up. Why would you want to transfer all your backup to all your computes and all your friends computers? Is your data so important you need 5 copies of it?

On another note, I currently use sparkshare, but I sometimes think there is no earthly reason to have a complete history of every single file, many of which are one-off sort of things. Its been a good short-term solution but again I don't see the need to have such a dramatic backup procedure.